Vapor-arc device



J n- 16, 1945- E. G. F. ARNOTT VAPOR-ARC DEVICE Filed March 7, 1942 INVENTOR E6. ARA/arr BY MJ HW ATTORNEY Patented Jan. :16, 1945 2 VAPOR-ARC DEVICE Edward G. F. Arnott, Upper Montclair, N. J., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 7, 1942, Serial No. 433,707

11 Claims.

This invention relates to vapor-arc electric discharge devices and more particularly applied in the present showing in connection with ignitrons, and is directed especially to the starter mechanism thereof.

The present method of initiating an arc in an ignitron, is by passing a current through an ignitor electrode dipping into a mercury pool. Such method allows the arc to be started with voltages of the order of 100-200 volts and ignitor currents of the order of 10-20 amperes. During operation of the ignitron the fluctuations in the surface of the mercury cause variations in the voltage and current required ,by the ignitor. For example, an ignitor which requires a maximum peak voltage of 100 Volts and a maximum peak current of 16 amperes will sometimes fire at 50 volts and 8 amperes. This same ignitor will fire approximately half the time below 75 volts and 12 amperes. These variations are thought to be mostly due shape of the mercury meniscus around the ignitor caused by random fluctuations in the surface of the mercury.

An object of the present invention is to overcome the deficiencies of prior art devices.

More explicitly, an object of the invention is to provide a constant starter gradient.

Another object is to provide a starter or igniting means not dipping into the fluid cathode.

A still further object of the invention is to provide for a starting discharge. situated for ready transfer to are formation between the cathode and anode.

Yet another object of the invention is to avoid the uncertainty of a starting discharge between parts, contact and meniscus whereof is indeterminately variable.

Other objectsof the invention will appear to those skilled in the art, in part by direct recitation thereof as the description proceeds, and in part set forth by inference from the context.

In the accompanying drawingwherein is disclosed a preferred embodiment of the invention, the figure illustrating the same is a sectional view of an ignitron or electrical discharge device having my improved starter incorporated therein.

In the specific embodiment of the invention illustrated in said drawing, the reference numeral l designates the body portion of the envelope or container which may be suitably formed, and preferably of metal, such as steel, iron, and so forth. It is shown with a closed integral bottom and with its upper margin shouldered outward at l I so as to provide an upper cylindrical rim l2 at the top of the container. A cup-shaped header [3 fits within said rim and rests on shoulder ll, being secured with a vacuum-tight seal by welding, brazing or other suitto the change in theable means. Appropriate gas or vapor atmos-,

phere for ionizing purposesis maintained in the sealed container, such as mercury vapor, hyclrogen, argon, helium, neon, krypton, xenon and others.

The header is shown provided with a plurality of eyelets M for sealed entry of the lead-in conductors. As shown, one eyelet I4 is substantially at the middle of the header and afiords sealed entry for a lead-in post l5 and electrical connection i6 thereto for the ignitron anode ll. At opposite sides of the central eyelet, two other similar eyelets provide sealed entry for lead-in rods l8, l9 from external connections Z0, 21, respectively.

On the lower ends of said rods, which extend to positions below anode ll and which are relatively rigid, are contact starter elements. As here shown an ignitor tip 22 is provided as the starter element on the lower end of rod l8, and. on the other rod I9 is a resilient contact element 23 which presses against said tip. Both the contact starterelements22, 23 are located above a mercury pool or other fluid cathode 2M situated in the bottom of container II]. The ignitor tip contact element is of a character to present high resistance and is preferably composed of appropriate materials from the group of graphite, boron, boron carbide and silicon carbide and the like in accordance with prevailing practice in manufacture of ignitor tips. The

shape of the ignitor tip element is preferably conical with the apex directed downward. The tip element accordingly presents a curvilinear face to the other element 23.

The other or resilient contact element 23 is preferably of metal having a high melting point, and for the purpose, tungsten has been selected. The tungsten contact element is in the form of a flat strip secured, as by knobs 25, 26, to and projecting transversely from the rod or conductor and is bent or flexed downward so that a part of its broader face engages against the conical surface of tip 22. Such engagement is preferably most pronounced toward the apex of the conical tip 22, thereby limiting engagement to line contact. By virtue of the arcuate shape enforced upon the tungsten stri severest contact with the contact element is toward the apex and is less intense away from the apex, the surfaces gradually departing or separating. The construction is accordingly one which simulates a meniscus contact, constituting a mechanical meniscus-like are starting means which has the most desirable advantage of constancy.

In the particular showing of input circuit .diagrammatically shown, the flexible contact element 23 is connected by way of rod 2| to an external circuit wire 21 in series with which is a resistance 28 on the opposite side of which connection is made to the cathode 24, as by connecting to the metallic container It! for the cathode, and from thence connection is made to the source of current supply 29. The other lead from the source of supply passes through a ballastin resistance 30 to the anode lead IS, a branch 3| being provided to the ignitor tip element through a suitable rectifier tube 32.

In operation, current flows down the ignitor element lead-in rod to element 22 and thence to the resilient element 23 producing a high voltage gradient at or near the point of contact between said elements 22, 23. Due to the high voltage gradient and sufficient voltage drop in the ignitor, an arc is started between the ignitor 22 and resilient strip element 23. This arc is above and out of direct contact with the mercury pool 2d but nearby to said pool or cathode. Consequential upon the voltage impressed between th anode l1 and cathode 24, this arc formed between the contact elements, is transferred to the nearby cathode so that a cathode spot is formed on the mercury and the positive end of the arc goes to the anode l1. Whereas heretofore it has been deemed essential to immerse the ignitor tip in the mercury and to rely upon the changeable meniscus of that material, I have found that as good or even better results are obtainable when not dipping the ignitor. By the present invention I provide cooperating ignitor elements above the mercury which make relatively unvarying contact at all times and one which will transfer an arc formed therebetween to the cathode separated therefrom.

While the invention has, for purposes of definiteness, been shown and described specifically in connection with its application to an ignitron, it is to be understood such showing is not to be taken as restrictive, the broad concept of means for starting an arc with low voltage between a cold cathode and an anode in the presence of gas or vapour, or even in vacuum.

I claim:

1. A vapor-arc electric discharge device comprising an anode and a cathode, and contact elements interposed between and separated electrically and physically within said'device from both said cathode and anode for initiating an are.

2. A vapor-arc electric discharge device comprising an anode and a cathode, and a pair of contact elements nearby to the cathode out of direct contact therewith and at different potential therefrom, said contact elements having limited contact and gradual departure from contact with each other for initiating an arc.

3. A vapor-arc electric discharge device comprising an anode and a fluid cathode, and arcinitiating means situated wholly above and -wholly out of electrical and physical contact within said device from said fluid cathode.

4. A vapor-arc electric discharge device comprising an anode and acathode, and a mechanical meniscus-like are starting means suspended in its entirety above and isolated electrically and physically within said device from the cathode and adapted to transfer the starting arc to form a cathode spot on the cathode and thereby initiate the arc discharge between the cathode and anode.

5. A vapor-arc electrode discharge device comprising an anode and a cathode, and a mechanbut as illustrative only, of

ical meniscus-like are starting means composed of constantly contacting elements having a high voltage gradient therebetween, means insulating said elements from electrical continuity within the device with said anode and cathode, and said elements being held at substantially constant distances from the cathode and anode.

6. A vapor-arc electric discharge device comprising an anode and a cathode, and a mechanical meniscus-like are starting means composed of dissimilar contacting elements one of which presses laterally into contact with the side of the other and said elements being suspended entirely out of electrical and physical contact within said device from both the anode and cathode, and said elements having a high voltage gradient therebetween.

7. A vapor-arc electric discharge device comprising an anode and a cathode, and a mechanical meniscus-like are starting means composed of dissimilar contacting elements one of which is of resilient metal and presses laterally into contact with the side of the other and said elements being suspended entirely out of electrical and physical contact within said device from both the anode and cathode, and said elements having a high voltage gradient therebetween.

8. A vapor-arc electric discharge device comprising an anode and a cathode, and a mechanical meniscus-like are starting means composed of dissimilar contacting elements one of which is a strip of resilient tungsten which presses laterally into contact with the side of the other and said elements being suspended entirely out of electrical and physical contact within the device from both the anode and cathode, and said elements having a high voltage gradient therebetween.

9. A vapor-arc electric discharge device comprising an anode and, a cathode, and a mechanical meniscus-like are starting means composed of dissimilar contacting elements of which one is of relatively high resistance and the other is of relatively low resistance, said elements maintaining contact with each other at all times and located in the space between and out of contact from both the anode and the cathode, and lead-in connections for said elements isolated within the device from said anode and cathode.

10. A vapor-arc electric discharge device comprising an anode and a cathode, and a mechanical meniscus-like are starting means composed of dissimilar contacting elements 01' which one is of relatively high resistance and having a curvilinear surface, and the other of which is a strip of low resistance making constant tangential contact with said curvilinear surface, both of said contacting elements being out of contact with the anode and cathode and each having a part thereof held in fixed position maintaining said elements in contacting relation.

11. A vapor-arc electric discharge device comprising an anode and a cathode, and contact elements interposed between and separated from both said cathode and anode for initiating an arc, said contact elements each having a part thereof held immovable and maintaining said elements in contacting relation, said immovable parts being electrically isolated within the device from said anode and cathode.

EDWARD G. F. ARNO'IT. 

